Filters for Photoshop - advice

I'm looking for some advice regarding possible plug in filters for Photoshop.
I'm looking for a filter to help make my images a little more atmospheric, I still use my Mamiya & Hasselblad for some work, but have mainly switched to Digital, and I'm looking for someway of producing images that give a nice atmospheric quality.

It's hard to describe, firstly the image must black & white, but I want a slightly soft and darker feel to the images, similar to the kind of image that used to be obtained via polaroid back on a Mamiya - if that helps...